This has been going on for years, but I just found it (thanks to my Opera star friend who's expanding my horizons). The idea is you take the San Diego metro trolley to a station, watch a dance performance, get on the train, go to another station, watch a dance, etc.
And it was fun! Especially fun for someone who's not into dance because the music, theme, choreographer for each of the pieces is different. Between the six I saw, there was be something for everyone. Heck, I liked four of them and I'm not a dance afficionado. (link to San Diego dance company)
They also do something similar in San Francisco which is this coming weekend (oct 17-18, 2009) - Check it out! (link).